Tuesday, 11 September, 2001, 00:12 GMT 01:12 UK Night shift link to heart problem The study compared people who worked days and nights

People who work nights are more prone to a dangerous heart condition - possibly because of the chronic stress caused by their work patterns, research suggests.

Scientists compared employees who worked shifts, including nights with others who worked normal daytime working hours.

They found shiftworkers were twice as likely to develop an irregular heartbeat.

And they said that could be because they suffer from "chronic stress" because of their work patterns.

The researchers say an irregular heartbeat can be an indicator a person will go on to develop more serious heart problems.

But UK heart experts said such abnormal rhythms were common place, and not necessarily an indication someone would develop coronary heart disease in the long term.

Previous studies have speculated that people working shifts are at an increased risk of heart disease because of disturbance to the circadian rhythm and changes to their behaviour.

And research published last year suggested the heart does not respond well to being made to work during the middle of the night, because the body is programmed to slow down during that time.

Comparison

The researchers looked at premature ventricular complexes (PVC), "early heartbeat problems", which occur when an irregular heartbeat occurs earlier than normal.

Doctors from Maastricht University in the Netherlands looked at 42 daytime workers and 83 shift workers who were all new to their jobs.

Their hearts were checked then, and subsequently after a year in the job.

It was found that both day and shift workers had slightly unfavourable changes to their heart rates.

But twice as many shift workers developed PVC compared to the day workers.

The more nights they worked, the more their risk increased.

This was true even when researchers took factors such as smoking, drinking coffee or alcohol, weight, age, sex and job stress into account.

Stress

Writing in the Occupational and Environmental Medicine journal the researchers, led by Dr Ludovic van Amelsvoort, say: "It might be that working at night is a chronic stressor."

They add: "We conclude that the increase in frequency of premature ventricular beats can be regarded as an indicator of unfavourable changes in the myocardial system, and should be regarded as a potentially important factor in the relation between shift work and the increased cardiovascular risk of disease."

A spokesman for the British Heart Foundation said: "There is some evidence to suggest that people who work on night shifts may be more vulnerable to stress.

"This could be attributed to changing sleeping patterns, emotional problems, and family commitments whilst juggling a varying work timetable, sometimes with little social support.

"In this small study the researchers found that those working shifts have an increased number of abnormal heart rhythms.

"In the majority of ectopic heartbeats, where the heart appears to "miss" a beat, it is due to increased emotional stress.

"These abnormal rhythms are common place, and do not necessarily indicate that someone is more likely to develop coronary heart disease in the long term."

-- Anonymous, September 11, 2001